Our ability to selectively focus attention on elements of our sensory environment is a critical cognitive function that enables us to enhance the processing of high priority stimuli. Both electrophysiological and hemodynamic brain imaging studies have implicated a network of brain areas in the frontal and parietal cortices as playing a role in imparting top-down attentional control to influence processing in low-level sensory cortices. In the previous grant period we used functional MRI (fMRI) and event-related potentials (ERPs) to help delineate the neural cascade of activations in specific regions in this control network during the voluntary orienting of attention, as well as various of the ways in which voluntary attention can modulate processing in the sensory cortices. However, many facets of the mechanisms by which attention facilitates our performance in the real world remain unclear. For example, most of our previous work focused on the mechanisms of voluntary attention when it was either directed in a sustained way to a particular location or stimulus channel, or when it needed to be oriented only relatively slowly. It seems likely, however, that for rapid spatial shifts of attention the neural control mechanisms differ in some important ways. Moreover, there are numerous other fundamental and ecologically important ways in which attention is invoked for enhancing the processing of relevant stimuli. For example, attentional shifts and attentional control can also be initiated by viewing an individual's eye gaze, by visual-popout stimuli, and by stimulus conflict, all of which appear to induce the engagement of attention in a faster and more automatized way than with endogenous instructional cues. However, the temporal cascade of the neural processes underlying attentional control and influence in these other circumstances has yet to be delineated. In the next period of this grant, we propose to continue our programmatic investigation of the neural mechanisms of attention with a new set of studies directed toward these other fundamental ways in which attentional control and influence is invoked. These will include study of: (1) the rapid shifting of both voluntary and gaze-cue-triggered visual spatial attention, (2) the shifting and focusing of spatial attention within a complex visual scene; and (3) the invocation of attention for detecting and resolving conflicting visual stimulus information. As before, we plan to combine ERPs, EEG, fMRI, and behavioral measures to perform these studies, with the aim to delineate the timing, sequence, and location of the neural processes and network dynamics involved in these cognitive functions, thereby gaining insight into the underlying mechanisms.